Phase diagram of hydrogen and a hydrogen-helium mixture at planetary conditions by Quantum Monte Carlo simulations

TL;DR

This paper uses Quantum Monte Carlo simulations to accurately determine the phase diagram and equation of state of hydrogen and hydrogen-helium mixtures at planetary conditions, improving upon previous methods.

Contribution

First QMC-based EOS for H and H-He mixtures at high temperature, highlighting helium's effect on hydrogen metallization pressure.

Findings

QMC provides more accurate phase diagrams than DFT.

Helium significantly influences hydrogen metallization.

Results aid in planetary interior modeling and calibration of other EOS methods.

Abstract

Understanding planetary interiors is directly linked to our ability of simulating exotic quantum mechanical systems such as hydrogen (H) and hydrogen-helium (H-He) mixtures at high pressures and temperatures. Equations of State (EOSs) tables based on Density Functional Theory (DFT), are commonly used by planetary scientists, although this method allows only for a qualitative description of the phase diagram, due to an incomplete treatment of electronic interactions. Here we report Quantum Monte Carlo (QMC) molecular dynamics simulations of pure H and H-He mixture. We calculate the first QMC EOS at 6000 K for an H-He mixture of a proto-solar composition, and show the crucial influence of He on the H metallization pressure. Our results can be used to calibrate other EOS calculations and are very timely given the accurate determination of Jupiter's gravitational field from the NASA Juno mission and the effort to determine its structure.